Achieving ultrahigh carrier mobilities and opening the band gap in two-dimensional Si2BN

Abstract

Recently, a two-dimensional (2D) Si₂BN monolayer material made of silicon, boron and nitrogen, was theoretically predicated and has attracted interest in the scientific community. Due to its 2D planar nature with high formation energy, Si₂BN monolayers can be flexible and strong like graphene and also exhibit captivating properties like those of other 2D materials. Motivated by this fascinating graphene-like monolayer of Si₂BN, we have investigated its structural and electronic properties based on first-principles calculations. The electronic band structure of pure Si₂BN shows metallic behaviour. We have discovered that the band gap of Si₂BN monolayer can be tuned to 102 meV by applying external electric fields and mechanical strain. The band gap opening occurs at 5% strain, where the bond angles between the nearest neighbours become nearly equal. The band gap opening occurs at a small external electric field of 0.4 V Å⁻¹. More interestingly, at room temperature, the electron mobility of Si₂BN is 4.73 × 10⁵ cm² V⁻¹ s⁻¹, which is much larger than that of graphene, while the hole mobility is 1.11 × 10⁵ cm² V⁻¹ s⁻¹, slightly smaller than the electron mobility. The ultrahigh carrier mobility of Si₂BN may lead to many novel applications in high-performance electronic and optoelectronic devices. These theoretical results suggest that the Si₂BN monolayer exhibits multiple effects that may significantly enhance the performance of Si₂BN based electronic devices.